Last updated: 12/24/2016

RV Electrical System Schematics

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Copyright 2002-2017 John Mayer. All rights reserved. For reuse policy see Reuse Policy

In this section I show some common wiring methods, detailed schematics, and address some of the things NOT to do. If you do not understand power issues do not attempt to do this work yourself. These designs are intended as examples - your actual design needs to take into account your needs and will likely differ from these. Nevertheless, implementing all or part of the preferred design should result in a good system for you. 

The Preferred Design
 
 

Inverter_w_subpanel.jpg (73470 bytes)This drawing provides an overview of the RV electrical system, and identifies major components used to support battery charging via: solar energy, the existing converter, and a new, high-powered battery charger contained in the inverter. Click on the drawings and they will expand into a new window.

 

Electrical input sources include a genset (either a portable, an RV mounted or a truck mounted), and shore power sources. Optionally, two main shore power sources are shown, controlled by a separate 50-amp transfer switch (TSO). These are intended to provide for a shore connection at the front of the 5er, and at the rear of the 5er. The existing converter is shown connected to an external power source (other than the RV) for optional use. This should never be plugged into the RV, but only to an external source via an extension cord.

 

Two designs are shown. The first is an inverter with a subpanel - typically used with a 50 amp coach.   The second is an inverter wired inline to the loadcenter. While far easier to implement, this is only applicable to a 30 amp RV - as discussed elsewhere. Inverters on the market today do not provide for passing through two legs of 50 amp power. Years ago, Xantrex had an inverter - the RS3000 - that did have a 50 amp dual leg transfer capability. This could be wired inline in a 50 amp RV. But this inverter is no longer manufactured.

 

Do not be confused by Magnum inverters that have "60 amp transfer switches". This is a total of 60 amps, either on a single input and/or output line, or on dual input/output  lines with 30 amps on each line. This is less than the 50 amps per line that is required for a 50 amp RV.

 

 

Inverter_inline.jpg (67197 bytes)


Assumptions:

 

  1. The RV is wired for 50-amp shore power. This is actually 2-50 amp lines, for a total of 100 amps available at the loadcenter, on 2 legs. All shore power is assumed to be using 6ga wire, except where noted.
  2. All the transfer switches are 50 amps.
  3. The inverter is an inverter/charger with a high output battery charger that replaces the RV converter for normal use.  The inverter has a pass thru power capability controlled by a 30-amp transfer relay.
Without the subpanel, when inverting the loadcenter is fully energized. It is up to the user to provide manual load management. In other words, don't turn on the air conditioner, electric hot water heater, or other large loads. Turn the breakers off, if you are prone to forget.


A 400-amp catastrophe fuse is used to protect against a short in the inverter DC line. It is placed either directly on the battery positive (if not placed in a fuse holder), or as close to the battery as possible if a fuse holder is used. Use the size appropriate for your inverter. See the wiring section for additional details and sources for the fuse and other components.

 

The shunt is a 500-amp shunt. It must be placed "downstream" of all loads to get an accurate measure of amps/amp hours. Place it between the distribution hub and the battery negative.

 

Use appropriate size welding cable for the DC inverter runs. Consult the inverter installation instructions. Do not use less than 2/0. I prefer to use 4/0 in most situations if the inverter is 2000 watts or more. The inverter should not be more than 10 feet from the battery (cable run).


Note 1

 

Optionally, I show two main shore power cables. When using an external generator (either portable or truck mounted) it is often convenient to have a shore power cable at the front of the rig. You simply use another 50-amp transfer switch - that way you can't have both "live" at once, or energize the other plug. This is obviously optional, but when wiring the transfer switches and deciding where to break into the main shore power cord you might consider leaving enough slack in the line to accommodate a future transfer switch if you decide not to do this right away.

 

 

Note 2

 

Distribution hubs are used for DC power connections. The existing house DC wires that feed the DC loadcenter are not shown in the drawing, but they should be moved to the distribution hubs. Typically, a wire goes from the converter directly to the battery, and another from the converter to the DC loadcenter. If you are leaving the converter in place you can remove the existing converter-to-battery wire, and splice a new wire into the line that goes from the battery charger output of the converter to the distribution hubs. (Your converter outputs may be different, but you get the idea...) The reason not to attach directly to the battery is that your battery monitor shunt will not pick up the power added/consumed if you bypass it. Loads must be upstream of the shunt. Not between the shunt and the battery bank.
 
The solar input and conventional converter inputs attach directly to the distribution hubs. You should attach all DC power input/outputs here. Nothing should attach directly to the battery except some of the instrumentation and monitoring lines, and possibly the DC catastrophe fuse (if not in a holder). If you have additional DC loads you are adding, you may want to add a small DC fuse center, which would also attach to the distribution hubs. I usually add one to support fusing for the solar lines, and some of the instrumentation lines which otherwise require inline fusing (which is not as neat, and not centrally located).

Instrumentation

 

In the diagrams, the dotted lines denote instrumentation lines. These are not shown in detail - there are multiple connection points and lines for each instrument. Follow the instructions.

 

Sometimes the solar controller will have a remote display, and sometimes the entire controller will mount where the display can be seen - it depends on the controller you use. If you have a choice, acquire the remote monitor for the solar controller. It will make the wire run for the solar line shorter. The solar line should be as short as possible to minimize voltage drop. I prefer to use 4 gauge for the drop from the roof to the battery bank - but run the interactive calculators for your specific panels and distance. Sometimes that means you have to trim the wire where it goes into the terminals on the solar controller in order to make it fit. That is OK. On the roof, I interconnect the solar panels with a minimum of 10 gauge - which is what the typical MC4 lines are.

 

If the inverter monitor panel has a running amp hour capability (also called cumulative amp hour) then you can eliminate the Trimetric amp hour meter, since it would be redundant. If not, you really need to know your accumulated amp hours (either positive or negative), since that is the best measure of the state-of-charge of your battery bank. You can buy a Trimetric meter, with 500 amp shunt, for under $175 at www.solarseller.com. If you are using a Xantrex inverter, the LinkPRO or LInkLIte meters contain an amp hour function. If you are using a Magnum inverter, then I prefer to add the Trimetric monitor instead of using the integrated BMK. Not only is it cheaper (slightly), but I think it functions better  and is more accurate. The advantage of using the BMK is that it is integrated into the existing inverter control panel.